In today's radio communications networks a number of different technologies are used, such as Long Term Evolution (LTE), LTE-Advanced, Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications/Enhanced Data rate for GSM Evolution (GSM/EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations. A radio communications network comprises Radio Base Stations (RBS) providing radio coverage over at least one respective geographical area forming a cell. The cell definition may also incorporate frequency bands used for transmissions, which means that two different cells may cover the same geographical area but using different frequency bands. User equipments (UE) are served in the cells by the respective radio base station and are communicating with respective radio base station. The user equipments transmit data over an air or radio interface to the radio base stations in uplink (UL) transmissions and the radio base stations transmit data over an air or radio interface to the user equipments in downlink (DL) transmissions. In e.g. High Speed Downlink Packet Access (HSDPA) systems a Radio Network Controller (RNC) may control the radio base stations.
Recently, Multiflow transmission was proposed in 3rd Generation Partnership Project (3GPP) for HSDPA. For multiflow transmission when connections to the user equipment are via different RBSs, the flow has to be split in the RNC. The connections may be referred to as ‘legs’. When HSDPA Flow Control is used in a traditional way the Capacity Allocation Control Frames (CA CF) define sending speed for both legs, which solves distribution of packets or Packet Data Units (PDU) among different legs. As HSDPA Flow Control is a proprietary solution and there may be other solutions, which do not only rely on credits indicated in High Speed-Downlink Shared Channel (HS-DSCH) CA CF. E.g. Active Queue Management (AQM) based congestion control solves flow control by propagating Iub interface or Medium Access Control-high speed (MAC-hs) or Medium Access Control-enhanced high speed (MAC-ehs) loss to end-user Transport Control Protocol (TCP). The main idea of an AQM based flow control is that the application level TCP is reused as congestion control solution. When congestion is detected then the application level TCP is informed by an Internet Protocol (IP) packet drop. This packet drop will be noticed by TCP and the TCP will react on this loss with rate reduction. The Iub interface connects the RBS and the RNC. The CA CF may include two Congestion Status Bits, however the values of these Congestion Status bits only indicate Transport Network Layer (TNL) congestion to be taken into account when distributing data to a user equipment still leading to a non-optimal packet distribution.